//
// Created by autulin on 2018/8/1.
//

#include <stdio.h>

#define         SIGN_BIT        (0x80)      /* Sign bit for a A-law byte. */
#define         QUANT_MASK      (0xf)       /* Quantization field mask. */
#define         NSEGS           (8)         /* Number of A-law segments. */
#define         SEG_SHIFT       (4)         /* Left shift for segment number. */
#define         SEG_MASK        (0x70)      /* Segment field mask. */
#define         BIAS            (0x84)      /* Bias for linear code. */
#define		CLIP            8159

#define		G711_A_LAW	(0)
#define		G711_MU_LAW	(1)
#define		DATA_LEN	(16)

static short seg_aend[8] = {
        0x1F, 0x3F, 0x7F, 0xFF,
        0x1FF, 0x3FF, 0x7FF, 0xFFF
};

static short seg_uend[8] = {
        0x3F, 0x7F, 0xFF, 0x1FF,
        0x3FF, 0x7FF, 0xFFF, 0x1FFF
};

unsigned char _u2a[128] = {
        /* u- to A-law conversions */
        1,1,2,2,3,3,4,4,
        5,5,6,6,7,7,8,8,
        9,10,11,12,13,14,15,16,
        17,18,19,20,21,22,23,24,
        25,27,29,31,33,34,35,36,
        37,38,39,40,41,42,43,44,
        46,48,49,50,51,52,53,54,
        55,56,57,58,59,60,61,62,
        64,65,66,67,68,69,70,71,
        72,73,74,75,76,77,78,79,
        81,82,83,84,85,86,87,88,
        89,90,91,92,93,94,95,96,
        97,98,99,100,101,102,103,104,
        105,106,107,108,109,110,111,112,
        113,114,115,116,117,118,119,120,
        121,122,123,124,125,126,127,128
};

unsigned char _a2u[128] = {
        /* A- to u-law conversions */
        1,3,5,7,9,11,13,15,
        16,17,18,19,20,21,22,23,
        24,25,26,27,28,29,30,31,
        32,32,33,33,34,34,35,35,
        36,37,38,39,40,41,42,43,
        44,45,46,47,48,48,49,49,
        50,51,52,53,54,55,56,57,
        58,59,60,61,62,63,64,64,
        65,66,67,68,69,70,71,72,
        73,74,75,76,77,78,79,79,
        80,81,82,83,84,85,86,87,
        88,89,90,91,92,93,94,95,
        96,97,98,99,100,101,102,103,
        104,105,106,107,108,109,110,111,
        112,113,114,115,116,117,118,119,
        120,121,122,123,124,125,126,127
};

static short search(int val, short *table, int size)
{
    int i;
    for (i = 0; i < size; i++) {
        if (val <= *table++)
            return (i);

    }
    return (size);
}

/*
 * linear2alaw() - Convert a 16-bit linear PCM value to 8-bit A-law
 *
 * linear2alaw() accepts an 16-bit integer and encodes it as A-law data.
 *
 *Linear Input CodeCompressed Code
 *---------------------------------------
 *0000000wxyza000wxyz
 *0000001wxyza001wxyz
 *000001wxyzab010wxyz
 *00001wxyzabc011wxyz
 *0001wxyzabcd100wxyz
 *001wxyzabcde101wxyz
 *01wxyzabcdef110wxyz
 *1wxyzabcdefg111wxyz
 *
 * For further information see John C. Bellamy's Digital Telephony, 1982,
 * John Wiley & Sons, pps 98-111 and 472-476.
 */
unsigned char linear2alaw(int pcm_val)/* 2's complement (16-bit range) */
{

    int mask;
    int seg;
    unsigned char aval;

    pcm_val = pcm_val >> 3;

    if (pcm_val >= 0) {
        mask = 0xD5;/* sign (7th) bit = 1 */
    } else {
        mask = 0x55;/* sign bit = 0 */
        pcm_val = -pcm_val - 1;
    }

    /* Convert the scaled magnitude to segment number. */
    seg = search(pcm_val, seg_aend, 8);

    /* Combine the sign, segment, and quantization bits. */

    if (seg >= 8)/* out of range, return maximum value. */
        return (unsigned char) (0x7F ^ mask);
    else {
        aval = (unsigned char) seg << SEG_SHIFT;
        if (seg < 2)
            aval |= (pcm_val >> 1) & QUANT_MASK;
        else
            aval |= (pcm_val >> seg) & QUANT_MASK;
        return (aval ^ mask);
    }

}

/*
 * alaw2linear() - Convert an A-law value to 16-bit linear PCM
 *
 */
int alaw2linear(unsigned char a_val)
{

    int t;
    int seg;

    a_val ^= 0x55;

    t = (a_val & QUANT_MASK) << 4;
    seg = ((unsigned)a_val & SEG_MASK) >> SEG_SHIFT;
    switch (seg) {
        case 0:
            t += 8;
            break;
        case 1:
            t += 0x108;
            break;
        default:
            t += 0x108;
            t <<= seg - 1;

    }
    return ((a_val & SIGN_BIT) ? t : -t);
}


/*
 * linear2ulaw() - Convert a linear PCM value to u-law
 *
 * In order to simplify the encoding process, the original linear magnitude
 * is biased by adding 33 which shifts the encoding range from (0 - 8158) to
 * (33 - 8191). The result can be seen in the following encoding table:
 *
 *Biased Linear Input CodeCompressed Code
 *---------------------------------------
 *00000001wxyza000wxyz
 *0000001wxyzab001wxyz
 *000001wxyzabc010wxyz
 *00001wxyzabcd011wxyz
 *0001wxyzabcde100wxyz
 *001wxyzabcdef101wxyz
 *01wxyzabcdefg110wxyz
 *1wxyzabcdefgh111wxyz
 *
 * Each biased linear code has a leading 1 which identifies the segment
 * number. The value of the segment number is equal to 7 minus the number
 * of leading 0's. The quantization interval is directly available as the
 * four bits wxyz.  * The trailing bits (a - h) are ignored.
 *
 * Ordinarily the complement of the resulting code word is used for
 * transmission, and so the code word is complemented before it is returned.
 *
 * For further information see John C. Bellamy's Digital Telephony, 1982,
 * John Wiley & Sons, pps 98-111 and 472-476.
 */
unsigned char linear2ulaw(short pcm_val)/* 2's complement (16-bit range) */
{
    short mask;
    short seg;
    unsigned char uval;

    /* Get the sign and the magnitude of the value. */
    pcm_val = pcm_val >> 2;
    if (pcm_val < 0) {
        pcm_val = -pcm_val;
        mask = 0x7F;
    } else {
        mask = 0xFF;
    }
    if (pcm_val > CLIP)
        pcm_val = CLIP;/* clip the magnitude */
    pcm_val += (BIAS >> 2);

    /* Convert the scaled magnitude to segment number. */
    seg = search(pcm_val, seg_uend, 8);

    /*
     * Combine the sign, segment, quantization bits;
     * and complement the code word.
     */
    if (seg >= 8)/* out of range, return maximum value. */
        return (unsigned char) (0x7F ^ mask);
    else {

        uval = (unsigned char) (seg << 4) | ((pcm_val >> (seg + 1)) & 0xF);
        return (uval ^ mask);
    }
}

/*
 * ulaw2linear() - Convert a u-law value to 16-bit linear PCM
 *
 * First, a biased linear code is derived from the code word. An unbiased
 * output can then be obtained by subtracting 33 from the biased code.
 *
 * Note that this function expects to be passed the complement of the
 * original code word. This is in keeping with ISDN conventions.
 */
short ulaw2linear(unsigned char u_val)
{
    short t;

    /* Complement to obtain normal u-law value. */
    u_val = ~u_val;

    /*
     * Extract and bias the quantization bits. Then
     * shift up by the segment number and subtract out the bias.
     */
    t = ((u_val & QUANT_MASK) << 3) + BIAS;
    t <<= ((unsigned)u_val & SEG_MASK) >> SEG_SHIFT;
    return ((u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS));
}

/* A-law to u-law conversion */
unsigned char alaw2ulaw(unsigned char aval)
{
    aval &= 0xff;
    return (unsigned char) ((aval & 0x80) ? (0xFF ^ _a2u[aval ^ 0xD5]) :
                            (0x7F ^ _a2u[aval ^ 0x55]));
}

/* u-law to A-law conversion */
unsigned char ulaw2alaw(unsigned char uval)
{
    uval &= 0xff;
    return (unsigned char) ((uval & 0x80) ? (0xD5 ^ (_u2a[0xFF ^ uval] - 1)) :
                            (unsigned char) (0x55 ^ (_u2a[0x7F ^ uval] - 1)));
}

int g711_encode(char *a_psrc, char *a_pdst, int in_data_len, unsigned char type)
{

    int i;
    short *psrc = (short *)a_psrc;
    int out_data_len = in_data_len / sizeof(short);

    if (a_psrc == NULL || a_pdst == NULL) {
        return (-1);
    }

    if (in_data_len <= 0) {
        return (-1);
    }


    if (type == G711_A_LAW) {
        for (i = 0; i < out_data_len; i++) {
            a_pdst[i] = (char)linear2alaw(psrc[i]);
        }
    } else {
        for (i = 0; i < out_data_len; i++) {
            a_pdst[i] = (char)linear2ulaw(psrc[i]);
        }
    }
    return (i);
}

int g711_decode(char *a_psrc, char *a_pdst, int in_data_len, unsigned char type)
{

    int i;
    short *pdst = (short *)a_pdst;
    int out_data_len = in_data_len / sizeof(char);

    if (a_psrc == NULL || a_pdst == NULL) {
        return (-1);
    }

    if (type == G711_A_LAW) {
        for (i = 0; i < out_data_len; i++) {
            pdst[i] = (short)alaw2linear((unsigned char)a_psrc[i]);
        }
    } else {
        for (i = 0; i < out_data_len; i++) {
            pdst[i] = (short)ulaw2linear((unsigned char)a_psrc[i]);
        }
    }

    return (i * sizeof(short));
}
